This invention relates to silicon carbide films/coatings and a process for preparing them. Particularly, the process involves depositing a layer of silicon carbide by a sputtering process using an electrically conductive silicon carbide target in an atmosphere having a low partial pressure of an inert gas and hydrogen. The coatings formed by the process of the present invention are particularly well suited for use as protective coatings on substrates which require a transparent coating.
Previously, silicon carbide thin-film layers have been deposited on the surface of a substrate to provide abrasion and chemical resistance. To be effective, the silicon carbide layers must offer chemical and physical resistance to degradation by heat, humidity, and a variety of chemicals, but transparency is also necessary for certain uses such as coating glass or optical recording medium.
U.S. Pat. No. 4,917,970 discloses a process for forming thin SiC films which are sufficiently transparent to be used in protecting a magneto optic recording medium. Nonreactive (i.e., no reactive gases present) direct current (DC) magnetron sputtering was used because it offered superior results when compared to evaporation techniques.
Although the coating of U.S. Pat. No. 4,917,970 is sufficiently transparent for laser read optical discs, it is desirable in the art to achieve a sputtered silicon carbide coating with a higher degree of transparency to allow thicker more protective coatings without a substantial loss of transparency.